(1) Field of the Invention
The present invention relates to a novel process for preparing N-glycolylneuraminic acid, particularly to a novel process for preparing N-glycolylneuraminic acid derivatives, precursors of N-glycolylneuraminic acid, from neuraminic acid derivatives and glycolic acid. N-glycolylneuraminic acid has recently drawn attention as a tumor-associated antigen and as a subject of embryological research.
(2) Description of the Prior Art
The process proposed by Schauer et al, Hoppe-Seyler's, Z.Physiol.Chem., vol. 351, 359-364 (1970), is known as a process for preparing an N-glycolylneuraminic acid derivative, which is a precursor for preparing N-glycolylneuraminic acid, from a neuraminic acid derivative and glycolic acid. In this process, dioxolandione (5) is obtained from glycolic acid (3) and phosgene (4), and then the dioxolandione (5) is reacted with a neuraminic acid derivative (6). ##STR4##
However this process has the following disadvantages:
Phosgene has to be used for the synthesis of dioxolandione (5) but it has strong toxicity and the handling thereof involves some risk;
Two steps are required for the reaction process; and
The yield of a N-glycolylneuraminic acid derivative, the object compound, is low (23%).
Hitherto, no process for preparing N-glycolylneuraminic acid derivatives by directly reacting neuraminic acid derivatives with glycolic acid has been known.